Postnatal Hydronephrosis with the following clinical findings: 1) APRPD is 10 to less than 15 mm, 2) central calyceal dilation may be present, but peripheral calyceal dilation is considered to increase risk, 3) renal parenchyma should have normal thickness and appearance, 4) the ureter is not seen, and 5) the bladder is normal. If there is central calyceal dilation but the APRPD is less than 10 mm, it is still considered UTD P1. (Adapted from: Hiep T. Nguyen, Carol B. Benson, Bryann Bromley, Jeffrey B. Campbell, Jeanne Chow, Beverly Coleman, Christopher Cooper, Jude Crino, Kassa Darge, C.D. Anthony Herndon, Anthony O. Odibo, Michael J.G. Somers, Deborah R. Stein; Multidisciplinary consensus on the classification of prenatal and postnatal urinary tract dilation (UTD classification system); Pediatric Urology; December 2014 Volume 10, Issue 6, Pages 982-998) [from
NCI]